Crystalline products can be manufactured by a number of known processes in which crystals are formed in a supersaturated fluid medium or mother liquor. Crystal purity depends in part on the rate of crystal growth. In order for crystallization processes to progress most efficiently, the processes typically depend on determining the onset of crystallization. Probes capable of backscatter analysis can be used to detect particles and thus to determine the onset of crystallization (see, for example, U.S. Pat. No. 4,672,218 to Chrisman); however, once crystallization begins, adjusting the system to adequately reduce the rate of crystallization can be difficult. Thus, a probe capable of better anticipating crystallization would achieve better process control in crystallization processes.